DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0066] First Embodiment

[0067] A first embodiment of this invention will now be described referring to FIGS. 5 through 11.

[0068] As shown in FIG. 5, a semiconductor manufacturing apparatus 41 has a vacuum transfer chamber 42, a process chamber 43 and a pre-pressurizing chamber or load-lock chamber (L/L chamber) 44. The semiconductor manufacturing apparatus 41 further has an internal transfer apparatus or robot 45 and an external transfer apparatus or robot 46.

[0069] The vacuum transfer chamber 42 is a rectangular parallelepiped. Inside the vacuum transfer chamber 42 is a vacuum. The internal transfer robot 45 is located in the vacuum transfer chamber 42. As shown in FIG. 6, the internal transfer robot 45 has two internal transfer arms 47a and 47b arranged hierarchically. The internal transfer arms 47a and 47b are supported in such a way as to be rotatable on a horizontal plane about an axis L1 positioned near the right-hand end in the vacuum transfer chamber 42 and to be vertically movable along the axis L1. The internal transfer arms 47a and 47b are moved vertically by an unillustrated actuator, and are turned about the axis L1 independently by two unillustrated actuators for rotation.

[0070] The internal transfer arms 47a and 47b each have at least one arcuate holding piece 48 for holding a workpiece or wafer W. The internal transfer robot 45 transfers wafers W, holding a single wafer W on each of the internal transfer arms 47a and 47b.

[0071] The process chamber 43 and the L/L chamber 44 are arranged along a turning locus of the internal transfer arms 47a and 47b. The process chamber 43 and the L/L chamber 44 have approximately circular plan shapes and a wafer W is held nearly in the center of each chamber. The positions of the process chamber 43 and the L/L chamber 44 are determined in such a way that the center of the wafer W held in each chamber matches with the arcuate locus that the center of the wafer W draws as it is transferred by the associated internal transfer arm 47a or 47b.

[0072] As the internal transfer arms 47a and 47b are turned and moved vertically, the wafers W are transferred between the L/L chamber 44 and the vacuum transfer chamber 42 and between the vacuum transfer chamber 42 and the process chamber 43. Unlike the conventional internal transfer robots 20 and 32 (see FIGS. 1 and 3), therefore, the entire internal transfer robot 45 need not be turned. Since the internal transfer arms 47a and 47b do not have a plurality of joints, they are easily controlled.

[0073] As shown in FIG. 5, two carriers 49 are located at predetermined locations in the semiconductor manufacturing apparatus 41. The carriers 49 retain a plurality of unprocessed wafers W lot by lot. In each carrier 49, the individual wafers W are stacked horizontally. The external transfer robot 46 transfers a wafer W between each carrier 49 and the L/L chamber 44. The external transfer robot 46 removes the unprocessed wafers W from the carriers 49 one after another and transfers them to the L/L chamber 44. The external transfer robot 46 transfers processed wafers W into the carriers 49 from the L/L chamber 44.

[0074] The external transfer robot 46 has a base 50 and two external transfer arms 51a and Sib arranged hierarchically. The external transfer arms 51a and Sib are movable along the base 50 and are rotatable on a horizontal plane. Each of the external transfer arms 51a and 51b has an arm section having a plurality of retractable joints and a hand section for holding a wafer W. The arm sections of the external transfer arms 51a and 51b are designed to be independently protractable and retractable. The protracting/retracting movements of the external transfer arms 51a and 51b permit wafers W to be exchanged without turning the external transfer arms 51a and 51b themselves. This decreases the time needed to transfer wafers W between the two carriers 49 and the L/L chamber 44.

[0075] The process chamber 43 and the L/L chamber 44 will now be discussed. FIG. 8 shows a state before transfer of wafers W to the L/L chamber 44 and the process chamber 43, and FIG. 9 shows wafers W transferred to the L/L chamber 44 and the process chamber 43.

[0076] The process chamber 43 is defined by a process-chamber hatch 52 formed integral with the top wall 42a of the vacuum transfer chamber 42 and a process-chamber stage 53. The process-chamber hatch 52 has a cylindrical shape with a top and has an inside diameter and height sufficient for processing a wafer W.

[0077] The process-chamber stage 53 is located inside the vacuum transfer chamber 42 via a circular insertion hole formed in the bottom wall 42b of the vacuum transfer chamber 42. The process-chamber stage 53 has a generally columnar shape whose diameter is about the same as the inside diameter of the process-chamber hatch 52. The process-chamber stage 53 is moved up and down by an unillustrated actuator. When the process-chamber stage 53 is moved to the position shown in FIG. 9 by the actuator, the top surface of the process-chamber stage 53 abuts the bottom surface of the top wall 42a, thereby tightly closing the process chamber 43. The position of the process-chamber stage 53 then is called a “close position”. The process-chamber stage 53 can be moved down to the position where it does not interfere with the rotational movement of the internal transfer arms 47a and 47b. The position of the process-chamber stage 53 then is called a “transfer position”.

[0078] A lift pin 54 provided on the process-chamber stage 53 is moved up and down by an unillustrated actuator. The lift pin 54 is provided at such a position as not to interfere with the transfer of wafers W by the internal transfer arms 47a and 47b. As the lift pin 54 is lifted to a predetermined height from the top surface of the process-chamber stage 53, it receives a wafer W from the internal transfer arm 47a or 47b.

[0079] When the lift pin 54 is moved down, the wafer W supported on the lift pin 54 is placed on the process-chamber stage 53 as indicated by a two-dot chain line in FIG. 8. The process-chamber stage 53 is moved up to the close position. Then, a predetermined process is performed on the top surface of the wafer W in the process chamber 43.

[0080] The process chamber 43 is provided with a plurality of gas valves 55 and an exhaust valve 56. Each gas valve 55 is connected to the process-chamber hatch 52. Various gases necessary for processing the wafer W in the process chamber 43 are fed via the gas valves 55. The gas valves 55 are selectively opened and closed in accordance with a processing step. The exhaust valve 56 is connected to a passage formed in the process-chamber stage 53. As the exhaust valve 56 is opened, the gas inside the process chamber 43 is discharged so that the inside of the process chamber 43 becomes a vacuum.

[0081] As shown in FIGS. 8 and 9, the vacuum transfer chamber 42 is connected to an unillustrated vacuum pump via an exhaust valve 57. As the exhaust valve 57 is opened, the gas inside the vacuum transfer chamber 42 is discharged so that the inside of the vacuum transfer chamber 42 becomes a vacuum.

[0082] The L/L chamber 44 is defined by an L/L hatch 61 and an L/L stage 62 which are arranged with the top wall 42a of the vacuum transfer chamber 42 in between. Formed in the top wall 42a is a passage 63 which connects the interior of the vacuum transfer chamber 42 to the area above the chamber 42. The passage 63 has a circular shape whose inside diameter is approximately the same as the inside diameter of the process-chamber hatch 52. The passage 63 is located on the locus that is drawn by the centers of wafers W transferred by the internal transfer arms 47a and 47b. The wafers W can pass through the passage 63 vertically while being positioned horizontally.

[0083] Like the process-chamber hatch 52, the L/L hatch 61 has a cylindrical shape with a top. The L/L hatch 61 has an inside diameter approximately the same as the inside diameter of the process-chamber hatch 52 and is high enough to retain a wafer W which has been transferred.

[0084] The L/L hatch 61 is so supported as to be movable upward by an unillustrated actuator. As this actuator is driven, the L/L hatch 61 is shifted between an unillustrated transfer position (upper position) and a close position (lower position) shown in FIGS. 8 and 9. With the L/L hatch 61 moved to the transfer position, the external transfer arms 51a and 51b do not contact the L/L hatch 61 and can move under the L/L hatch 61. At the close position, the L/L hatch 61 closes the passage 63.

[0085] The L/L stage 62 is formed in a disk shape having an outside diameter such as to be able to close the passage 63 formed in the top wall 42a. The L/L stage 62 is supported on a support which is inserted in the vacuum transfer chamber 42 from below through a circular insertion hole formed in the bottom wall 42b of the vacuum transfer chamber 42. The support is moved upward or downward as an unillustrated actuator is driven. The L/L stage 62 is therefore vertically movable in the vacuum transfer chamber 42. The position of the L/L stage 62 is switched between the transfer position shown in FIG. 8 and the close position shown in FIG. 9.

[0086] At the close position, the L/L stage 62 closes the passage 63 and does not interfere with the rotational movement of the internal transfer arms 47a and 47b.

[0087] A wafer holder 64 is provided on the top surface of the L/L stage 62 and holds a wafer W at a predetermined height from the top surface of the L/L stage 62. The wafer holder 64 has a shape which does not interfere with the external transfer arms 51a and 51b and the internal transfer arms 47a and 47b. When the L/L stage 62 is at the transfer position shown in FIG. 8, wafers W are transferred between the L/L stage 62 and the process chamber 43 by the internal transfer arms 47a and 47b. When the L/L stage 62 is at the close position shown in FIG. 9, wafers W are transferred between the L/L stage 62 and the carriers 49 by the external transfer arms 51a and 51b.

[0088] With the L/L stage 62 at the close position, the external transfer arms 51a and 51b (see FIG. 5) can receive a wafer W held by the wafer holder 64. With the L/L stage 62 at the transfer position, the internal transfer arms 47a and 47b can receive a wafer W held by the wafer holder 64.

[0089] A purge valve 66 is connected via a pipe to the L/L hatch 61. An exhaust valve 65 is connected to a pipe passage provided in the L/L stage 62. The passage 63 is closed by the L/L hatch 61 and the L/L stage 62 which are positioned at the close position. When the exhaust valve 65 is opened in this state, the passage 63 and the L/L hatch 61 are pumped down to a vacuum state inside by the unillustrated vacuum pump.

[0090] When the L/L stage 62 is moved down to the transfer position, the wafer W held by the wafer holder 64 is transferred into the vacuum transfer chamber 42 in a vacuum state. The wafer W is picked up by the internal transfer arm 47a (47 b) and carried into the process chamber 43 (FIG. 5). The wafer W on the arm 47b (47 a) is placed on the wafer holder 64 and is carried into the passage 63 as the L/L stage 62 is moved upward. At this time, since the passage 63 is closed by the L/L hatch 61, the interior of the vacuum transfer chamber 42 is kept in a vacuum state.

[0091] When the purge valve 66 is opened with the passage 63 closed by the L/L hatch 61 and the L/L stage 62, a nitrogen gas is supplied to the L/L chamber 44 from an unillustrated gas source. The supply of nitrogen gas increases the pressures in the L/L hatch 61 and the passage 63 nearly to atmospheric pressure. When the L/L hatch 61 is shifted to the transfer position, the wafer W held by the wafer holder 64 of the L/L stage 62 is held by the external transfer arm 51a (51 b). The wafer W held by the external transfer arm 51b (51 a), on the other hand, is placed on the wafer holder 64 of the L/L stage 62 which is at the transfer position. Since the lower portion of the passage 63 is closed by the L/L stage 62 at this time, the insides of the vacuum transfer chamber 42 and the process chamber 43 are kept in a vacuum state.

[0092] In other words, when the L/L stage 62 and the L/L hatch 61 are moved to the transfer position, the L/L stage 62 closes the passage 63 and the upper portion of the L/L stage 62 is released, so that the wafer W can be transferred under the atmospheric state while keeping the inside of the vacuum transfer chamber 42 in a vacuum state. When the L/L stage 62 and the L/L hatch 61 are moved to the close position, on the other hand, the L/L hatch 61 closes the passage 63 so that the wafer W can be transferred into the vacuum transfer chamber 42 while keeping the L/L chamber 44 in a vacuum state. In this semiconductor manufacturing apparatus 41, the passage 63, the L/L hatch 61 and the L/L stage 62 constitute the L/L chamber 44 as a pre-pressurizing chamber. The L/L chamber 44 allows wafers W to be transferred between the carriers 49 and the vacuum transfer chamber 42 without opening the process chamber 43 to the atmosphere.

[0093] As shown in FIG. 7, the semiconductor manufacturing apparatus 41 includes a computer 71 as its core. The computer 71 is connected to a display device 72, an input device 73, a storage device 74, the external transfer robot 46 and the internal transfer robot 45. The computer 71 is also connected to various actuators and various valves 55-57, 65 and 66 (see FIGS. 8 and 9) for the L/L chamber 44 and the process chamber 43.

[0094] The storage device 74 stores recipes or process steps for manufacturing wafers W. The recipes comprises process program codes associated with process sequences in the process chamber 43 and control parameters (control target values such as the temperature, the pressure, the type of gas, the flow rate of gas and the time). The computer 71 controls both robots 45 and 46, and the various actuators and various valves 55-57, 65 and 66 for the L/L chamber 44 and the process chamber 43 in accordance with the process program codes described in the recipes.

[0095] The transfer operation of the internal transfer robot 45 will now be discussed with reference to FIGS. 10A-10< /bold>D.

[0096] FIGS. 10A to 10D illustrate the movements of the internal transfer arms 47a and 47b for exchanging a wafer W1 in the process chamber 43 with an unprocessed wafer W2. In FIG. 10A, the processed wafer W1 is held by the lift pin 54 in the process chamber 43, and the unprocessed wafer W2 is held by the lower internal transfer robot 47b of the internal transfer robot 45. A wafer W3 which is to be processed next to the wafer W2 is held by the wafer holder 64 in the L/L chamber 44.

[0097] The computer 71 exchanges the processed wafer W1 with the unprocessed wafer W2 according to the following steps (11) to (13).

[0098] (11) The computer 71 moves the process-chamber stage 53 to the transfer position shown in FIG. 8. Then, the computer 71 turns the upper internal transfer arm 47a of the internal transfer robot 45 to an exchange position where the wafer W1 in the process chamber 43 is to be held (FIGS. 10A and 10B).

[0099] (12) As shown in FIG. 10C, the computer 71 simultaneously drives the upper and lower internal transfer arms 47a and 47b to exchange the wafer W1 in the process chamber 43 with the unprocessed wafer W2. That is, the computer 71 moves the upper internal transfer arm 47a upward and causes the arm 47a to hold the processed wafer W1. Next, the computer 71 turns the upper internal transfer arm 47a holding the processed wafer W1 to a buffer position between the process chamber 43 and the L/L chamber 44. At the same time as turning the upper internal transfer arm 47a, the computer 71 turns the lower internal transfer arm 47b holding the unprocessed wafer W2 to the exchange position on the process chamber 43 side from the buffer position.

[0100] (13) The computer 71 moves the lower internal transfer arm 47b down and places the wafer W2 on the lift pin 54 in the process chamber 43, then turns the lower internal transfer arm 47b to the buffer position (FIG. 10D).

[0101] Through the above steps, the computer 71 exchanges the processed wafer W1 in the process chamber 43 with the unprocessed wafer W2 in the vacuum transfer chamber 42. Thereafter, the computer 71 moves the process-chamber stage 53 upward. Then, the computer 71 initiates a wafer process on the unprocessed wafer W2 according to the recipes.

[0102] In a transfer sequence similar to the one just discussed for the process chamber 43, the computer 71 exchanges the unprocessed wafer W3 held by the wafer holder 64 in the L/L chamber 44 with the processed wafer W1 held by the upper internal transfer arm 47a. That is, the computer 71 exchanges the processed wafer W2 in the vacuum transfer chamber 42 with the unprocessed wafer W3 in the L/L chamber 44 in the same way as the above-described transfer sequence.

[0103] Next, the wafer transfer operation by the semiconductor manufacturing apparatus 41 will be described according to a transfer sequence shown in FIG. 11.

[0104] It is assumed here that an unprocessed wafer W is retained in the L/L chamber 44 and the upper internal transfer arm 47a of the internal transfer robot 45 is holding a processed wafer W. It is also assumed that a process on a wafer W is under way in the process chamber 43. It is further assumed that the first external transfer arm 51a of the external transfer robot 46 is holding an unprocessed wafer W which has been taken out of the carrier 49.

[0105] The computer 71 performs wafer transfer via the L/L chamber 44 according to steps S11a to S15a in FIG. 11, and performs wafer transfer via the process chamber 43 according to steps S11b and S12b.

[0106] First, the computer 71 carries out a “Wf exchange step” in the L/L chamber 44 (step S11a< /italic>). In the Wf exchange step, the lower internal transfer arm 47b receives the unprocessed wafer W retained in the L/L chamber 44. The processed wafer W held by the upper internal transfer arm 47a is placed on the wafer holder 64 in the L/L chamber 44.

[0107] Next, the computer 71 opens the purge valve 66 to feed the nitrogen gas into the L/L chamber 44 to make the pressure in the L/L chamber 44 nearly equal to the atmospheric pressure (step S12a< /italic>). By this time, the process on the wafer W in the process chamber 43 has already been completed. At the same time, the computer 71 performs a “Wf exchange step” in the process chamber 43 (step S11b< /italic>). In this step, the computer 71 exchanges the unprocessed wafer W held by the lower internal transfer arm 47b with the processed wafer W in the process chamber 43 according to the sequence in FIGS. 10A to 10D. Then, the computer 71 performs a predetermined process on the wafer W retained in the process chamber 43 (step S12b< /italic>).

[0108] After the pressure in the L/L chamber 44 rises nearly to the atmospheric pressure, the computer 71 performs a “Wf exchange step” in the L/L chamber 44 under atmospheric pressure (step S13a< /italic>). In this step, the computer 71 exchanges the unprocessed wafer W held by the first external transfer arm 51a with the processed wafer W in the L/L chamber 44.

[0109] When the exchange is completed, the computer 71 manipulates the exhaust valve 65 to discharge the gas out of the L/L chamber 44 and set the L/L chamber 44 in a vacuum state (step S14a< /italic>). When the inside of the L/L chamber 44 becomes a vacuum state, the computer 71 executes a “Wf exchange step” in the L/L chamber 44 in a manner similar to that of step S11a< /italic>. That is, the computer 71 exchanges the unprocessed wafer W in the L/L chamber 44 with the processed wafer W that the lower internal transfer arm 47b has received in step S11b.

[0110] When the time needed for wafer processing is short, therefore, the “Wf exchange step” in the process chamber 43 will not be carried out until the “Wf exchange step” in step S15a is finished. That is, it is the wait time from the point of completion of the wafer processing in step S12b to the point where exchange of wafers W becomes possible.

[0111] The first embodiment has the following advantages.

[0112] (1) The semiconductor manufacturing apparatus 41 has the internal transfer robot 45 which transfers wafers W by the rotational and vertical movements of the internal transfer arms 47a and 47b. The process chamber 43 and L/L chamber 44 are arranged on the rotational locus of the internal transfer arms 47a and 47b. As a result, the vacuum transfer chamber 42 only has a size large enough to permit the rotation of the internal transfer arms 47a and 47b. It is thus possible to make the site area or footprint of the vacuum transfer chamber 42 smaller than that of the prior art.

[0113] (2) The semiconductor manufacturing apparatus 41 transfers wafers W in the same number of steps as those of the transfer sequence of the conventional apparatus 31 shown in FIG. 3. Unlike the conventional apparatuses 11 and 31, the semiconductor manufacturing apparatus 41 need not rotate the internal transfer robot 45 to change the transfer direction in order to start the transfer sequence for wafer exchange. The throughput of the semiconductor manufacturing apparatus 41 is therefore higher than those of the conventional apparatuses 11 and 31.

[0114] (3) The operations that the semiconductor manufacturing apparatus 41 carries out to transfer wafers W are simple rotation and up-and-down elevation, and the protraction and retraction of the internal transfer arms 47a and 47b needed in the conventional transfer sequences illustrated in FIGS. 2 and 4 are not necessary. This simplifies the control for the transfer sequence. Although the semiconductor manufacturing apparatus 41 has fewer drive shafts by one than the conventional apparatuses 11 and 31, it can demonstrate the same functions as the conventional ones.

[0115] Second to seventh embodiments of this invention will be described below. The same reference numerals are given to those components which are the same as the aforementioned components of the first embodiment.

[0116] Second Embodiment

[0117] As shown in FIG. 12, a semiconductor manufacturing apparatus 81 according to a second embodiment has a vacuum transfer chamber 82, a process chamber 43 and two pre-pressurizing chambers (load-lock (L/L) chambers) 84a and 84b. The semiconductor manufacturing apparatus 81 further has an internal transfer robot 45 and an external transfer robot 46.

[0118] The vacuum transfer chamber 82 is a rectangular parallelepiped. The internal transfer robot 45 is located in nearly the center of the vacuum transfer chamber 82. The internal transfer robot 45 has two internal transfer arms 47a and 47b arranged hierarchically. The arms 4,7a and 47b are rotatable on a horizontal plane about an axis L1 positioned on the right-hand side in the vacuum transfer chamber 82 in FIG. 12. The arms 47a and 47b are further vertically movable along the axis L1 (see FIG. 6).

[0119] As shown in FIGS. 13 and 14, the process chamber 43, the upper L/L chamber 84a and the lower L/L chamber 84b are located on the rotational locus of the internal transfer arms 47a and 47b. The lower L/L chamber 84b is located under the upper L/L chamber 84a. The site area or footprint of the L/L chambers 84a and 84b in the second embodiment is smaller than that of the L/L chambers 14 and 15 of the conventional semiconductor manufacturing apparatus 11 or 31 shown in FIGS. 1 or 3.

[0120] The internal transfer robot 45 transfers wafers W between the L/L chambers 84a and 84b and the vacuum transfer chamber 82 and between the vacuum transfer chamber 82 and the process chamber 43 only by the rotational and vertical movements of the internal transfer arms 47a and 47b, as per the first embodiment. Unlike the conventional internal transfer robots 20 and 32 (see FIGS. 1 and 3), therefore, the whole internal transfer robot 45 need not be rotated. As the internal transfer arms 47a and 47b do not have a plurality of joints, they are easily controlled.

[0121] The structures of the L/L chambers 84a and 84b will be discussed below.

[0122] The upper L/L chamber 84a, like the L/L chamber 44 in the first embodiment, is positioned above the vacuum transfer chamber 82. This upper L/L chamber 84a includes an upper L/L hatch 85a and an upper L/L stage 86a. The upper hatch 85a and the upper stage 86a are arranged with the top wall 82a of the vacuum transfer chamber 82 in between.

[0123] Formed in the top wall 82a is an upper passage 87a which connects the inside and outside of the vacuum transfer chamber 82 to each other. The upper passage 87a has a circular shape whose center matches with a predetermined point on the locus that is drawn by the centers of wafers W transferred by the internal transfer arms 47a and 47b. The inside diameter of the upper passage 87a is approximately the same as that of the process-chamber hatch 52, which is greater than the diameter of the wafers W.

[0124] The upper hatch 85a has a cylindrical shape with a top which is similar to the shape of the process-chamber hatch 52. The upper hatch 85a has an inside diameter approximately the same as that of the process-chamber hatch 52 and is high enough to retain a wafer W which has been transferred.

[0125] The upper hatch 85a is movable upward by an unillustrated actuator, so that the upper hatch 85a can be shifted between a transfer position (not shown) and a close position shown in FIGS. 13 and 14. With the upper hatch 85a at the transfer position, the upper passage 87a is released. The transfer position of the upper hatch 85a is set in such a way as not to interfere with the external transfer arms 51a and 51b. Therefore, the external transfer arms 51a and 51b can move under the upper hatch 85a. When the upper hatch 85a is shifted to the close position, on the other hand, the upper hatch 85a contacts the top surface of the top wall 82a, thus closing the upper passage 87a.

[0126] The upper stage 86a has a disk shape whose outside diameter is large enough to be able to close the lower portion of the upper passage 87a. The upper stage 86a is movable vertically in the vacuum transfer chamber 82 by an unillustrated actuator. The position of the upper stage 86a can be switched between the transfer position shown in FIG. 13 and the close position shown in FIG. 14.

[0127] When the upper stage 86a is at the transfer position, the turning internal transfer arms 47a and 47b can pass above the upper stage 86a. That is, the transfer position of the upper stage 86a is so set as not to interfere with the rotating internal transfer arms 47a and 47b. When the upper stage 86a is at the close position, the upper stage 86a abuts the bottom surface of the top wall 82a, thus closing the upper passage 87a.

[0128] An upper wafer holder 88a is provided on the top surface of the upper stage 86a and is designed to not interfere with the external transfer arms 51a and 51b and the internal transfer arms 47a and 47b. The upper wafer holder 88a holds a wafer W at a predetermined height from the top surface of the upper stage 86a. Wafers W are transferred by the external transfer arms 51a and 51b and the internal transfer arms 47a and 47b. Specifically, when the upper stage 86a is at the transfer position shown in FIG. 13, wafers W are transferred by the internal transfer arms 47a and 47b, and when the upper stage 86a is at the close position shown in FIG. 14, the wafers W are transferred by the external transfer arms 51a and 51b.

[0129] The height of the upper wafer holder 88a is so set that the external transfer arms 51a and 51b (see FIG. 5) can receive a wafer W held by the upper wafer holder 88a when the upper stage 86a is at the close position. The upper stage 86a can move down to the transfer position where the internal transfer arms 47a and 47b can receive a wafer W held by the upper wafer holder 88a.

[0130] The upper hatch 85a is provided with an exhaust valve 89a and a purge valve 90a. The upper passage 87a is closed by the upper hatch 85a and the upper stage 86a which are positioned at the close position. When the exhaust valve 89a is opened in the closed state, the inside of the L/L chamber 84a is pumped to a vacuum state by an unillustrated vacuum pump.

[0131] When the upper stage 86a is moved down to the transfer position after the inside of the L/L chamber 84a has reached a vacuum state, the wafer W held by the upper wafer holder 88a is transferred into the vacuum transfer chamber 82. The wafer W is picked up by the internal transfer arm 47a (47 b) from the upper wafer holder 88a in the vacuum transfer chamber 82 and carried into the process chamber 43 in FIG. 5. The wafer W on the arm 47b (47 a) is placed on the upper wafer holder 88a. As the upper stage 86a moves upward, the wafer W is transferred into the upper L/L chamber 84a. Since the upper passage 87a is closed by the upper hatch 85a at this time, the inside of the vacuum transfer chamber 82 is kept in a vacuum state.

[0132] When the purge valve 90a is opened with the upper passage 87a closed by the upper hatch 85a and the upper stage 86a, a nitrogen gas is supplied from an unillustrated gas source. The supplied nitrogen gas increases the pressures in the upper hatch 85a and the upper passage 87a nearly to the atmospheric pressure. Then, the upper hatch 85a is shifted to the transfer position. Consequently, the external transfer arm 51a (51 b) holds the wafer W held by the upper wafer holder 88a. The wafer W held by the external transfer arm 51b (51 a), on the other hand, is placed on the upper wafer holder 88a of the upper stage 86a at the transfer position. Since the upper passage 87a is closed by the upper stage 86a at this time, the insides of the vacuum transfer chamber 82 and the process chamber 43 are kept in a vacuum state.

[0133] As the upper passage 87a is closed by the upper stage 86a in the semiconductor manufacturing apparatus 81, the wafer W can be transferred under the atmospheric state while keeping the inside of the vacuum transfer chamber 82 in a vacuum state. Because the upper passage 87a is closed by the upper hatch 85a, the wafer W can be transferred into the vacuum transfer chamber 82 under a vacuum condition while keeping the inside of the vacuum transfer chamber 82 in a vacuum state. As apparent from the above, the upper passage 87a, the upper hatch 85a and the upper stage 86a constitute the upper L/L chamber 84a as a pre-pressurizing chamber, which can allow wafers W to be transferred between the carriers 49 and the vacuum transfer chamber 82 without opening the process chamber 43 to the atmosphere.

[0134] The lower L/L chamber 84b is provided under the upper L/L chamber 84a. The lower L/L chamber 84b is formed symmetrical to the upper L/L chamber 84a with the vacuum transfer chamber 82 in between. The lower L/L chamber 84b includes a lower L/L hatch 85b and a lower L/L stage 86b. The lower hatch 85b and the lower stage 86b are arranged with the bottom wall 82b of the vacuum transfer chamber 82 in between.

[0135] Formed in the bottom wall 82b is a lower passage 87b which connects the inside and outside of the vacuum transfer chamber 82 to each other. The lower passage 87b has a circular shape whose center lies at a predetermined point on the locus that is drawn by the centers of wafers W transferred by the internal transfer arms 47a and 47b. The inside diameter of the lower passage 87b is approximately the same as that of the upper passage 87a.

[0136] The shape of the lower hatch 85b is approximately the same as that of the upper hatch 85a. The lower hatch 85b is located symmetrical to the upper hatch 85a with the vacuum transfer chamber 82 in between. The lower hatch 85b is moved under the vacuum transfer chamber 82 by an unillustrated actuator. The lower hatch 85b is shiftable between the transfer position and the close position (neither shown).

[0137] When the lower hatch 85b is shifted to the transfer position, the external transfer arms 51a and 51b can move above the lower hatch 85b. That is, the transfer position of the lower hatch 85b is set so as not to interfere with the external transfer arms 51a and 51b. When the lower hatch 85b reaches the close position, the lower hatch 85b abuts the bottom surface of the bottom wall 82b, thus closing the lower passage 87b.

[0138] The lower stage 86b has a disk shape whose outside diameter is large enough to close the lower portion of the lower passage 87b. The lower stage 86b is movable vertically in the vacuum transfer chamber 82 by an unillustrated actuator. The position of the lower stage 86b can be switched between the transfer position (upper position) and the close position (lower position) (neither shown).

[0139] When the lower stage 86b is at the transfer position, the turning internal transfer arms 47a and 47b can pass above the lower stage 86b. That is, the transfer position of the lower stage 86b is set so as not to interfere with the rotating internal transfer arms 47a and 47b. When the lower stage 86b is at the close position, the lower stage 86b abuts the top surface of the bottom wall 82b, thus closing the lower passage 87b.

[0140] A lower wafer holder 88b is provided on the bottom surface of the lower stage 86b. The lower wafer holder 88b holds a wafer W at a predetermined height from the bottom surface of the lower stage 86b. Wafers W are transferred by the external transfer arms 51a and 51b and the internal transfer arms 47a and 47b. The lower wafer holder 88b is formed into such a shape so as not to interfere with the movements of the external transfer arms 51a and 51b and the internal transfer arms 47a and 47b. When the lower stage 86b is at the transfer position, wafers W are transferred by the internal transfer arms 47a and 47b, and when the lower stage 86b is at the close position, the wafers W are transferred by the external transfer arms 51a and 51b.

[0141] When the lower stage 86b is at the close position, as shown in FIG. 13, the external transfer arms 51a and 51b (see FIG. 5) can receive the wafer W that is held by the lower wafer holder 88b. When the lower stage 86b is at the transfer position, the internal transfer arms 47a and 47b can receive the wafer W that is held by the lower wafer holder 88b.

[0142] The lower hatch 85b is provided with an exhaust valve 89b and a purge valve 90b. The lower passage 87b is closed by the lower hatch 85b and the lower stage 86b which are positioned at the close position. When the exhaust valve 89b is opened with the lower passage 87b closed, the insides of the lower passage 87b and the lower hatch 85b are pumped to a vacuum state by the unillustrated vacuum pump.

[0143] When the lower stage 86b is moved to the transfer position, the wafer W held by the lower wafer holder 88b is transferred into the vacuum transfer chamber 82 in a vacuum state. The internal transfer arm 47a (47 b) receives the wafer W from the lower wafer holder 88b and transfers it to the process chamber 43. The wafer W on the internal transfer arm 47b (47 a) is placed on the lower wafer holder 88b. As the lower stage 86b moves downward, the wafer W is transferred into the lower passage 87b. Since the passage 87b is closed by the lower hatch 85b at this time, the inside of the vacuum transfer chamber 82 is kept in a vacuum state.

[0144] When the purge valve 90b is opened with the lower passage 87b closed by the lower hatch 85b and the lower stage 86b, a nitrogen gas is supplied to the lower L/L chamber 84b from the unillustrated gas source. This nitrogen gas increases the pressure in the lower L/L chamber 84b nearly to the atmospheric pressure. When the lower hatch 85b is shifted to the transfer position, the external transfer arm 51a (51 b) holds the wafer W held by the lower wafer holder 88b of the lower stage 86b. The wafer W held by the external transfer arm 51b (51 a) is placed on the lower wafer holder 88b of the lower stage 86b at the transfer position. Because the lower passage 87b is closed by the lower stage 86b at this time, the inside of the vacuum transfer chamber 82 and the process chamber 43 are kept in a vacuum state.

[0145] In other words, the lower passage 87b is closed by the lower stage 86b in the semiconductor manufacturing apparatus 81, so that the wafer W can be transferred under atmospheric pressure while maintaining the inside of the vacuum transfer chamber 82 in a vacuum state. Because the lower passage 87b is closed by the lower hatch 85b and becomes a vacuum, the wafer W can be transferred under a vacuum state. As apparent from the above, the lower passage 87b, the lower hatch 85b and the lower stage 86b constitute the lower L/L chamber 84b as a pre-pressurizing chamber, which allows wafers W to be transferred between the carriers 49 and the vacuum transfer chamber 82 without opening the process chamber 43 to the atmosphere.

[0146] The transfer operation of the sem